Tawatchai Anukul, 66, died on August 30 a day after he was detained by the DSI. He was accused of illegally issuing title deeds worth about Bt10 billion.
Police are investigating whether Tawatchai died as a result of suicide, which the DSI claimed, or he was murdered.
Metropolitan Police Division 2 commander Maj-General Charoen Srisasalak yesterday said police planned to summon the doctor who performed the autopsy.
An autopsy report from the Institute of Forensic Medicine has been submitted to police.